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Doctor Jessica Rigg

Candidature

Jessica MowleGraduated PhD 2017

Thesis Title

Microbial influences on the conservation and recovery of the Wollemi Pine

Research Project

The iconic and endangered Wollemi pine (Wollemia nobilis) is a monotypic species known from only one population of fewer than 100 trees. The population is situated within Wollemi National Park in the Greater Blue Mountains Heritage Area.

The rare and endangered status of Wollemi pine, in addition to an extensive fossil history indicates that Wollemi pine is of great taxonomic significance.

The small population size and low genetic variability of Wollemi pine means that the population has a ubiquitous susceptibility to plant pathogens, particularly Phytophthora cinnamomi.

In 2005, the deadly root-rot pathogen Phytophthora cinnamomi was found to have infected at least three trees at the site, with disease severity possibly linked to stress.

Translocation was proposed as a conservation strategy to establish 'back-ups' to the wild population, but knowledge regarding the environmental and biotic requirements of Wollemi pine planted in new environments is very limited. This knowledge is necessary to identify land that is appropriate for strategic conservation for targeted translocation.

It is also essential to develop effective strategies for propagating stress-tolerant plant material, particularly with regard to drought, heat-stress, and pathogens. With many tree species, one of the most important limitations to their introduction or reintroduction is the presence of microbial partners.

Wollemi pine grows on shallow soils of poor nutrient status and high acidity; therefore, we expect Wollemi pine to be highly dependent on mycorrhizal fungi and bacteria that contribute to nutrient cycling.

This research will fill important knowledge gaps and lead to guidelines that enhance translocation outcomes, a critical next step identified by the Wollemi pine recovery plan.

Research Project Supervisors

A/Professor Jeff Powell, Professor Ian Anderson, Professor Brajesh Singh, Dr Catherine Offord

Publications

Lee MR, Powell JR, Oberle B, Cornwell WK, Lyons M, Rigg JL, Zanne AE, (2019) 'Good neighbors aplenty: fungal endophytes rarely exhibit competitive exclusion patterns across a span of woody habitats', Ecology, vol.100, no.9, DOI: 10.1002/ecy.2790

Rigg JL, Offord CA, Zimmer H, Anderson IC, Singh BK, Powell JR, (2017) 'Conservation by translocation: establishment of Wollemi pine and associated microbial communities in novel environments', Plant and Soil, vol.411, no.s 1-2, pp 209-225

Rigg JL, Offord CA, Singh BK, Anderson I, Clarke S, Powell JR, (2016) 'Soil microbial communities influence seedling growth of a rare conifer independent of plant-soil feedback', Ecology, vol.97, no.12, pp 3346-3358

Rigg JL, Offord CA, Singh BK, Anderson IC, Clarke S, Powell JR, (2016) 'Variation in soil microbial communities associated with critically endangered Wollemi pine affects fungal, but not bacterial, assembly within seedling roots', Pedobiologia, vol.59, no.1-2, pp 61-71